Making and breaking of phosphorus–phosphorus bonds

In contrast to their mostly unstable isolobal carbon counterparts, oligophosphanide anions, such as M(cyclo-P5tBu4) (M=Li, Na) and M2(P4R4) [M=Na, K; R=Ph, tBu, 2,4,6-Me3C6H2 (Mes)], have unique features, depending on their composition and structure, and are highly suitable building blocks for the synthesis of phosphorus-rich metal compounds. However, alkali metal oligophosphanediides are highly reactive and highly reducing, and a major problem is their tendency for disproportionation in reactions with electrophiles. This, however, can also give rise to a fascinating chemistry of making and breaking of P–P bonds. On the other hand, neutral cyclooligophosphines, such as cyclo-(P5Ph5), are suitable stable ligands for the formation of phosphorus-rich metal complexes.

[3]Ferrocenophanes with the bisphosphanotetryl bridge: inorganic rings on the way to tetrylenes

A series of [3]ferrocenophanes with functional P-E-P motifs (E = group 14 fragments) is reported. Out of these, the silicon compounds with the general formula Fe(C5H4PtBu)2SiXY (XY = Cl2, Br2, I2, H2, HCl) have been characterized by spectroscopic means and the bonding situation was analyzed using X-ray crystallography and quantum chemical calculations. Despite the two stereogenic phosphanyl centers, most of the [3]ferrocenophanes have been obtained as single isomers in the course of stereospecific reactions. The corresponding stannylene Fe(C5H4PtBu)2Sn has been obtained in the form of its dimeric adduct.

Different transmetallation behaviour of [M(P4HR4)] salts toward rhodium(I) and copper(I) (M = Na, K; R = Ph, Mes; Mes = 2,4,6-Me3C6H2)

[K(2)(P(4)Mes(4))] (1) or [Na(2)(THF)(4)(P(4)Mes(4))] (2) (Mes = 2,4,6-Me(3)C(6)H(2)) reacts with one equivalent of HCl and subsequently with 0.5 equivalents of [{RhCl(cod)}(2)] (cod = 1,5-cyclooctadiene) to give a mixture of rhodium complexes, from which [Rh(P(4)HMes(4))(cod)] (3) and the secondary product [Rh(2)(micro-P(2)HMes(2))(mu-PHMes)(cod)(2)] (4) were isolated and characterised by X-ray diffraction studies. Alternatively, the reaction of [K(2)(P(4)Ph(4))] (5) or [Na(2)(THF)(5)(P(4)Ph(4))] (6) with one equivalent of HCl and subsequently with one equivalent of [CuCl(PCyp(3))(2)] (Cyp = cyclo-C(5)H(9)) gave the complex [Cu(4)(P(4)Ph(4))(2)(PH(2)Ph)(2)(PCyp(3))(2)] (7), presumably via disproportionation of the monoanion (P(4)HPh(4))(-).